The dental restoration of a partially or wholly edentulous patient with artificial dentition is typically done in two stages. In the first stage, an incision is made through the gingiva to expose the underlying bone. An artificial tooth root, usually a dental implant, is placed in the jawbone for integration. The dental implant generally includes a threaded bore to receive a retaining screw holding mating components therein. During the first stage, the gum tissue overlying the implant is sutured and heals as the osseointegration process continues.
Once the osseointegration process is complete, the second stage is initiated. Here, the gum tissue is re-opened to expose the end of the dental implant. A healing component or healing abutment is fastened to the exposed end of the dental implant to allow the gum tissue to heal therearound. Preferably, the gum tissue heals such that the aperture that remains generally approximates the size and contour of the aperture that existed around the natural tooth that is being replaced. To accomplish this, the healing abutment attached to the exposed end of the dental implant has the same general contour as the gingival portion of the natural tooth being replaced. It should be noted that the healing abutment can be placed on the implant immediately after the implant has been installed and before osseointegration.
During the typical second stage of dental restoration, the healing abutment is removed and an impression coping is fitted onto the exposed end of the implant. This allows an impression of the specific region of the patient's mouth to be taken so that an artificial tooth is accurately constructed. Thus, in typical dental implant systems, the healing component and the impression coping are two physically separate components. Preferably, the impression coping has the same gingival dimensions as the healing component so that there is no gap between the impression coping and the wall of the gum tissue defining the aperture. Otherwise, a less than accurate impression of the condition of the patient's mouth is taken. The impression coping may be a “pick-up”-type impression coping or a “transfer”-type impression coping, both known in the art. After these second stage processes, a dental laboratory creates a prosthesis to be permanently secured to the dental implant from the impression that was made.
In addition to the method that uses the impression material and mold to manually develop a prosthesis, systems exist that utilize scanning technology to assist in generating a prosthesis. A scanning device is used in one of at least three different approaches. First, a scanning device can scan the region in the patient's mouth where the prosthesis is to be placed without the need to use impression materials or to construct a mold. Second, the impression material that is removed from the healing abutment and the surrounding area is scanned to produce the permanent components. Third, a dentist can scan the stone model of the dental region that was formed from the impression material or scan the stone model.
Three basic scanning techniques exist: laser scanning, photographic imaging, and mechanical sensing. Each scanning technique is used or modified for any of the above-listed approaches (a scan of the stone model, a scan of the impression material, or a scan in the mouth without using impression material) to create the prosthesis. After scanning, a laboratory can create and manufacture the permanent crown or bridge, usually using a computer-aided design (“CAD”) package.
The utilization of a CAD program, as disclosed in U.S. Pat. No. 5,338,198 (Wu), whose disclosure is incorporated herein by reference, is one method of scanning a dental region to create a three-dimensional model. Preferably, after the impression is taken of the patient's mouth, the impression material or stone model is placed on a support table defining the X-Y plane. A scanning laser light probe is directed onto the model. The laser light probe emits a pulse of laser light that is reflected by the model. A detector receives light scattered from the impact of the beam with the impression to calculate a Z-axis measurement. The model and the beam are relatively translated within the X-Y plane to gather a plurality of contact points with known locations in the X-Y coordinate plane. The locations of several contact points in the Z-plane are determined by detecting reflected light. Finally, correlating data of the X-Y coordinates and the Z-direction contact points creates a digital image. Once a pass is complete, the model may be tilted to raise one side of the mold relative to the opposite vertically away from the X-Y plane. Subsequent to the model's second scan, the model may be further rotated to allow for a more accurate reading of the model. After all scans are complete, the data may be fed into a CAD system for manipulation of this electronic data by known means.
Photographic imaging can also be used to scan impression material, a stone model, or directly in the mouth. For example, one system takes photographs at multiple angles in one exposure to scan a dental region, create a model, and manufacture a prosthetic tooth. As disclosed in U.S. Pat. No. 5,851,115 (Carlsson), whose disclosure is incorporated herein by reference, this process is generally initiated with the process of taking a stereophotograph with a camera from approximately 50 to 150 mm away from the patient's mouth. The stereophotograph can involve a photograph of a patient's mouth already prepared with implantation devices. Correct spatial positioning of the dental implants is obtained by marking the implant in several locations. The resulting photograph presents multiple images of the same object. The images on the photographs are scanned with a reading device that digitizes the photographs to produce a digital image of the dental region. The data from the scanner is electronically transmitted to a graphical imaging program that creates a model that is displayed to the user. After identification of the shape, position, and other details of the model, the ultimate step is the transmission of the data to a computer for manufacturing.
A third scanning measure uses mechanical sensing. A mechanical contour sensing device, as disclosed in U.S. Pat. No. 5,652,709 (Andersson), whose disclosure is incorporated herein by reference, is another method used to read a dental model and produce a prosthetic tooth. The impression model is secured to a table that may rotate about its longitudinal axis as well as translate along the same axis with variable speeds. A mechanical sensing unit is placed in contact with the model at a known angle and the sensing equipment is held firmly against the surface of the model by a spring. When the model is rotated and translated, the sensing equipment can measure the changes in the contour and create an electronic representation of the data. A computer then processes the electronic representation and the data from the scanning device to create a data array. The computer further compresses the data for storage and/or transmission to the milling equipment.